This type of observation unit is used in a storage such as an incubator, and includes a mounting table on which a container containing a sample such as a cell together with a culture medium is to be mounted, a driving mechanism that moves the mounting table along a horizontal plane, and an observation device that observes the sample in the container to acquire an observed image of the sample. The observation device can vertically move with respect to the mounting table. In this observation unit, the mounting table is moved along the horizontal plane, and the observation device is vertically moved to adjust a focus, so that the sample in the container is observed.
Further, in the observation unit, coordinates and the focus position of the sample are recorded as sample information in a memory. One or more samples can be observed based on the sample information on a certain cycle by using the observation device, and a time lapse operation of acquiring the observed image of the sample can be performed at each observation.
When a predetermined period elapses from the start of the time lapse operation, the culture medium in the container is soiled with growth of the sample, and nutrition contained in the culture medium decreases. Accordingly, the culture medium in the container needs to be exchanged or resupplied. When this exchange or resupply operation (hereinafter referred to as “exchange operation”) is performed, the container is moved from the mounting table to another place. After completion of the exchange operation, the container is mounted on the mounting table again. At this time, it is difficult to mount the container at the same position and orientation as the position and orientation before the exchange operation of the culture medium on the mounting table. For this reason, the position and orientation of the container vary before and after the exchange operation of the culture medium. Accordingly, the sample information recorded in the memory becomes invalid, and the sample information must be set again in order to continue the time lapse operation.
In contrast, a window may be provided in the storage, and by putting a hand from the window, the exchange operation of the culture medium may be performed without moving the container on the mounting table. However, an operational range via the window is narrow and thus, it is difficult to perform the exchange operation of the culture medium without moving the container. Alternatively, the container may be provided with a marker, and when the position and orientation of the container is displaced before and after the exchange operation of the culture medium, coordinates and the focus position of the sample, which correspond to the coordinates and the focus position recorded in the memory, may be calculated based on the position of the marker. The available container will be limited to a specific container having the marker, thereby type of the container is limited.
Thus, an observation unit including a tray base attached to the driving mechanism, and a container tray detachably attached to the tray base has been proposed (refer to, for example, Patent Document 1). Specifically, the container tray is positioned at a predetermined position with respect to the tray base by a pin. The container tray has an insertion hole for inserting the container thereinto, and an inner surface of the insertion hole has a plurality of protrusions. Accordingly, when the container is inserted into the insertion hole, each of the protrusions is elastically deformed, so that a biasing force (elastic force) is applied from each of the protrusions toward the container. As a result, the container is held by the plurality of protrusions to fix the container to the container tray.
As another technique of fixing the container to the container tray, a technique of fixing the container by using a slide pin is proposed (refer to, for example, Patent Document 2). Specifically, the container tray has an insertion hole for inserting the container thereinto, an inner surface of the insertion hole has a horizontal hole, and the slide pin is slidably stored in the horizontal hole. The slide pin is biased toward the inner side of the insertion hole by a spring, and a front end of the slide pin protrudes from an inner surface of a hole for the container. A knob for a sliding operation is attached to the slide pin. A plurality of fixing pins are provided on the inner surface of the insertion hole.